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Before coming to this institute, I worked as a practicing clinical psychologist for ten years, where I helped young patients with severe mental illnesses, such as psychoses and developmental disorders. A concern that I had during this time was that most patients waited a very long time, five or more years, until symptoms became extremely severe, before seeking treatment. I saw patients in their late twenties to early thirties, but I often learned that it was in their adolescence, when they were in junior high or high school, when their mental problems began. I realized that if we were able to understand and help patients during adolescence, we could have a greater effect on their future well-being and happiness.

Well, of course, I also really like science. When I started working as a psychologist, clinical psychology wasn’t evidence-based. Psychoanalysis was dominant. Japan was behind other countries where evidence-based treatments such as cognitive behavioral therapy were being used.

Depression and anxiety are emotional problems. Under similar aversive conditions, some people become depressed while others don’t. People who are able to focus on things they enjoy are more likely to be able to bounce back from depressing situations. For people who can’t bounce back, it can become a vicious cycle. So, people have different tendencies, and through discussions with psychologists, patients figure out what tendencies they have and how they should modify their behaviors to improve their emotions. By experimenting during therapy, they find out what treatments work for them. That is cognitive behavioral therapy (CBT). There are many randomized control trials that prove that CBT works. So, my interest in research started from my desire to integrate evidence-based therapies into Japanese psychological treatments.

When I was a practicing psychologist, I worked with medical doctors and studied brain science, so in my mind, clinical practice and research weren’t so separate. At the institute, now, I focus on adolescent cohort studies. I focus on big data from cohorts to identify what factors contribute to recovery from depression, and what factors function as barriers to recovery. I think this research will contribute to better clinical treatments.

One difficulty with mental health is that it is difficult to visualize the problems and identify their causes. For example, we know that depression is far more common in women compared to men, but we didn’t know when these gender differences started and what their causes are. Depression is pretty low in children in general, and increases rapidly in adolescents, but there are few reliable studies in adolescents. We are dealing with this deficit by performing large scale longitudinal studies of teens in Tokyo. In this current study, we collaborated with a team doing similar studies in the UK to determine at what age gender differences start in adolescence. Our paper was likely accepted in Lancet Child and Adolescent Health because we used similar protocols and could reliably compare the results from two different societies. We found that in both countries, adolescent girls had more depression than adolescent boys and this difference increased by age. Interestingly, gender differences started slightly earlier in London (11-12 years of age) compared to Tokyo (between 11 and 14 years of age), and increased much more rapidly, 4 times as quickly, in London as in Tokyo. Our study found that gender differences in depression are caused by social factors, so they might be preventable through social and structural changes.

We have a collaboration with King’s College in London, and the Wellcome Trust is funding us for five years in a continuation project, Bridging Divides, to identify the causes of this gender mental health gap, by comparing Japan and London. What is special about this project is that we share our data with the young people we interviewed to obtain their viewpoints and interpretation in group discussions. We hear what the young people themselves are feeling and experiencing to develop hypotheses together that we can then test. Using this approach, we’ve identified several candidate mechanisms for gender differences in depression.

One is that girls are more concerned about how they are perceived, how their physical appearance is judged, and what body types they have compared to boys. This is intensified in the age of smartphones and Instagram and contributes to the mental health gap. Second, interpersonal relationships and social networks are more important to girls during adolescence and they are more sensitive to isolation and loneliness and this also contributes to the mental health gap.

We will continue our cohort study to find out how our subjects change as they grow older. But we’ve gained a lot of data so we’re now planning on moving onto the next step which for us is interventional studies. We’re collaborating with the Tokyo Metropolitan Government and going to schools to try to decease depression by changing the environment at schools. School is a critical environment where adolescents spend about 15,000 hours. If that environment is terrible, of course teens will become depressed. And we’ve confirmed from our teen cohort studies that school is a very important factor influencing mental health, so I believe that interventions in school are a worthwhile endeavor. Thus, one of my plans for the future is to conduct interventional studies to alter the environment in schools to improve adolescent mental health.